function person(){
    var person = prompt("who are you ?")
    if(person==="admin" || person==="Admin"){
        var pass = prompt("hello admin T please enter youre password ..")
        if(pass === "themaster" || pass === "Themaster"){
            alert("wellcome")
        }else{
            alert("passworn not correct  !!!")
        }
    }else{
        alert("i dont know you")
    }
}

<script>
        var user = prompt("who is there?");
        if ( user === "admin"){
            var pass = prompt("please type your pass:");
            pass === "themaster" ? alert("well come") : alert("wrong password");
        }else {
            alert("i don't know you...");
        }
</script>

<script>
         var user = ["admin","Admin","ADMIN"];
         var pass = "mohamad۱";
         var GetUser = prompt("ENTER YOUR USERNAME:")
         if (GetUser === user){
             var GetPass = prompt("ENTER YOUR PASSWORD:")
             if(GetPass === pass){
                 alert("welcome boss!")
             }
             else{
                 alert("password is wrong")
             }
         }else{
             alert("Username Not Found")
         }
</script>

داخل شرط اولم وقتی کلمه
Admin
وارد میشه
undefined
میزنه
در صورتی که ادمین با 
a
کوچک هیچ ایرادی نداره

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